The pressure at which typical gas distribution systems supply gas may vary according to a number of factors. These factors may include, for example, the demands placed on the system, the climate, the source of supply, and/or other factors. However, most end-user facilities equipped with gas appliances such as furnaces, ovens, etc., require the gas to be delivered in accordance with a predetermined pressure, and at or below a maximum capacity of the end-user appliance. Therefore, process fluid regulators are implemented in these distribution systems in order to ensure that the delivered gas meets the requirements of the end-user facilities. Process fluid regulators are also used to regulate the delivery of liquids to achieve similar functionalities. However, fluid regulators can become unstable and begin to flutter, or rapidly oscillate, undesirably in response to changes in pressure of the process fluid.
FIG. 1 shows a common process fluid regulator 10. The fluid regulator 10 includes a regulator body 12, a control element 14, and an actuator 16. The regulator body 12 defines a fluid flow path 18, a fluid inlet 20, a fluid outlet 22, and an orifice 24. The orifice 24 is operatively disposed between the fluid inlet 20 and the fluid outlet 22. The fluid flow path 18 extends from the fluid inlet 20, through the orifice 24, and to the fluid outlet 22. The control element 14, such as a valve disk or plug, shifts to regulate the flow of fluid along the fluid flow path 18 through the orifice 24. The actuator 16 is operatively connected to the regulator body 12 and the control element 14 to control the position of the control element 14 relative to the orifice 24. The actuator includes an actuator housing 26, a diaphragm 28 disposed inside the housing 26, and an actuator linkage 30 operatively connecting the diaphragm 28 to the control element 14. The diaphragm 28 separates the housing 26 into a first chamber 32 and a second chamber 34. The first chamber 32 is hydraulically connected to the fluid outlet 22, such as by one or more fluid conduits 35 extending from the first chamber 32 to a location in the fluid flow path 18 downstream of the orifice 24, to sense a fluid pressure at the fluid outlet 22. The second chamber 34 is hydraulically connected to the surrounding ambient atmosphere. The linkage 30 includes a lever 36 having a first end operatively connected to the diaphragm 28 and a second end operatively connected to a valve stem 38 operatively connected to the control element 14. Movement of the diaphragm 28 in response to pressure changes at the fluid outlet 22 causes the linkage to shift the valve stem 38, and thereby the control element 14, in a manner to maintain a the process fluid pressure within a preselected range at the fluid outlet 22.
The actuator housing 26 is formed of a first or spring case 40 and a second or diaphragm case 42 secured together, such as with one or more bolts connecting respective outer flanges of the first and second cases 40, 42. The diaphragm 28 has an outer peripheral edge clamped between the outer flanges of the spring case 40 and the diaphragm case 42. The first chamber 32 is defined at least partly by the diaphragm 28 and the diaphragm case 42. The second chamber 34 is defined at least partly by the spring case 40 and the diaphragm.
A first or exhaust vent 44 is formed in the spring case 40 of the housing 26 and extends into the second chamber 34. The exhaust vent 44 includes a bore 46 extending from an inlet 48 to an outlet 59. The bore 46 is defined by a sleeve 50 extending along an outer surface of the spring case 40. The inlet 48 is defined by a first orifice through the spring case 40. The outlet 49 is defined by a distal end of the sleeve 50. The exhaust vent 44 hydraulically connects the second chamber 34 to the surrounding ambient atmosphere to allow the second chamber 34 to be maintained at approximately the same pressure as the surrounding ambient atmosphere.
A stabilizer valve 52 in the form of a normally-closed check valve is disposed in the exhaust vent 44. The stabilizer valve 52 is disposed at the inlet 48 and includes a stabilizer, such as a seal disk 54, a stabilizer guide, such as a rod 56, and a spring 58. The rod 56 depends from the inner surface of the sleeve 50 and extends through an aperture through the seal disk 54. The seal disk 54 is slidingly disposed on the rod 56. The spring 58 seats against the inner surface of the sleeve 50 and the seal disk 54 and biases the seal disk 54 into sealing engagement with an outer periphery of the inlet 48. The seal disk 54 slides up along the rod 56 and compresses the spring 58 when air pressure inside the second chamber 34 exceeds a set point force of the spring 58.
The stabilizer valve 52 stabilizes movement of the diaphragm 28 and the control element 14 in response to rapid changes in the outlet fluid pressure at the fluid outlet 22. For example, without the stabilizer valve 52, rapid changes in the outlet fluid pressure may cause undesirable oscillation, or flutter, of the diaphragm 28 and the control element 14. The stabilizer valve 52 helps to reduce such oscillations by limiting exhausting of air through the exhaust vent 44 until the air inside the second chamber 34 reaches a minimum backpressure sufficient to overcome the bias force of the spring 58.
It may sometimes be desirable to adjust a set point pressure or backpressure setting of the stabilizer valve 52. In the present arrangement, it may be difficult to adjust the backpressure setting without disassembling the spring case 40 from the diaphragm case 42 in order to access the various components of the stabilizer valve 52. This may require complete shutdown of the process line being controlled by the fluid regulator 10, which may be undesirable at a time that the backpressure setting needs to be adjusted.
A second or control vent 68 is formed in the diaphragm case 42 of the housing 26 and extends into the first chamber 32. The control vent 68 includes an aperture 70 through the diaphragm case 42 and a socket 72. The socket 72 is defined by sleeve 74 on the outer surface of the diaphragm case 42. Preferably, the sleeve 74 is an integral portion of the diaphragm case 42. The sleeve 74 has a first end surrounding the aperture 70, a second end spaced distal from the aperture, and interior threads 76 adjacent the second end. Fluid, such as air or liquid, from inside the first chamber 32 may pass through the aperture 70 and the socket 72. In some applications, the control vent 68 is closed, such as with a plug (not shown) threadedely engaged into the socket 72 at the interior threads 76 at the second end of the sleeve. In other applications, the control vent 68 is operatively connected to a process line, for example, by a conduit 78 operatively connecting the sleeve 74 to a process pipe (not shown) operatively connected to the fluid outlet 22. In this arrangement fluid pressure inside the first chamber 32 can equalize with fluid pressure at a downstream point in the process pipe through the aperture 70 and the conduit 78.